The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air and fuel mixture within cylinders to drive pistons, which produces drive torque. Air flow into gasoline engines is regulated via a throttle. More specifically, the throttle adjusts a throttle area, which increases or decreases air flow into the engine. As the throttle area increases, the air flow into the engine increases. A fuel control system adjusts the rate that fuel is injected to provide a desired air/fuel mixture to the cylinders. Increasing the amount of air and fuel provided to the cylinders increases the torque output of the engine.
Engine control systems have been developed to control engine torque output to achieve a desired torque. Traditional engine control systems, however, do not control the engine torque output as accurately as desired. Further, traditional engine control systems do not provide a rapid response to control signals or coordinate engine torque control among various devices that affect the engine torque output.
Exhaust gases exit the engine through an exhaust manifold and are treated by an exhaust system. Engine systems often include an exhaust gas recirculation (EGR) system to reduce emissions. EGR systems return the exhaust gases to an intake manifold to be drawn into the cylinders. The exhaust gases contain unburned fuel. Oxygen levels in the exhaust gases are lower than oxygen levels in the air/fuel mixture before combustion.
Returning the exhaust gases to the cylinders tends to limit the amount of oxygen available for combustion and increase the manifold air pressure. Limiting the oxygen available for combustion lowers combustion temperatures and reduces emissions. Increasing the manifold air pressure reduces pumping losses of the engine, thereby improving fuel economy.
Debris build-up within the EGR system restricts the flow of exhaust and minimizes the effectiveness of the EGR system. Thus, an EGR diagnostic test may be performed to determine when the EGR flow is restricted. The EGR diagnostic test may include opening an EGR valve to increase the EGR flow and monitoring pressure levels in the intake manifold.